Key to me is something that's easy to carry without being crushable, self-contained so that it doesn't spill out while you're eating it, not requiring refrigeration for the better part of a day, and something that you can eat without getting it all over your hands or otherwise being messy to eat. Burritos or wraps work pretty well, particularly if they don't have a lot wet squishy stuff in them. They don't crush like sandwiches and they seem to be easier to fit in a vest, etc. I like jerky as well, but you have to make sure you've got plenty of drinking water (or whatever ) with you.